【摘要】 本文通过凝胶电泳分析以及电镜的观察,检测灰色链毒菌质粒DNA转化前后的给体、受体和转化子中质粒的存在情况,结合链霉素合成能力的变化证明,链霉素产生菌——灰色链霉菌No.45(给体)中存在两个质粒pSG1(19×10~6道尔顿)和pSG2(2.3×10~6道尔顿)。高温消除质粒的、丧失合成链霉素能力的、气生菌丝受抑制的突变体No.45—3(受体)中只有pSG2,说明高温漓除的质粒是pSG1。以结霉素抗性为筛选标记,通过质粒DNA转化而重新获得合成链霉素能力的转化子TrNo.30(转化子)中,既检测到pSG2,也检测到pSG1。这就进一步证明与链霉素生物合成有关的质粒是pSG1,而不是pSG2。上述电泳分析结果又为电镜观察所证实。更多还原

【Abstract】 The characterization of plasmids of three strains of S.griseus was studied by agarose gel electrophoresis analysis and E.M.observation.Our results have indicated that S.griseus No.45 (donor),a streptomycin producer,involves two plasmids,pSGl (19X106 dalton) and pSG2 (2.3X106 dalton),while the other,S.griseus No.45-3 (recipient),a plasmid-cured mutant with the loss of ability of streptomycin biosynthesis,still harbours pSG2; the third,S.griseus Tr.No.30 (trannsformant obtained by the pksmid DNA transformation using Lmr as a selective marker,regaines the ability of streptomycin synthesis and resumes the plasmid pSGl.This provides further evidence that there are two plasmids (pSGl and pSG2) present in S.griseus No.45 and it is pSGl not pSG2 that is closely related to the biosynthesis of streptomycin in this strain.更多还原